Wrought aluminous metal article



Dec. 3, 1963 E. H. HOLLINGSWORTH 3,113,002

WROUGHT ALUMINOUS METAL ARTICLE Filed June 16, 1960 ATTORNEY United States Patent 3,113,002 WROUGHT ALUMINOUS METAL ARTHJLE Ernest H. Hollingsworth, New Kensington, Pa, assignor to-Aluruinum Company of America, Pittsburgh, Pa, a corporation of Pennsylvania Filed June 16, 1960, Ser. No. 36,577 8 Claims. (Cl. 29195) This invention relates to aluminous articles, and has as an object to provide aluminous articles exhibiting an artistic pattern that is of a permanent nature, and therefore suitable for use in architectural and other decorative applications.

It is another object of the invention to provide a heterogeneous wrought aluminous product having Zones of varying chemical composition, and which reveal a variegated pattern upon suitable surface treatment.

'In accordance with the present invention, the foregoing and other objects and advantages are obtained to a particularly high degree with my new product formed from a mixture of aluminous particulate of varying chemical composition. The particulate may be consolidated under heat and pressure to form a compact that is subsequently worked, or the particulate may be charged directly to a compression chamber and a bonded body extruded therefrom. Employing particulate varying in chemical composition results in a bonded metal body having a non-uniform or heterogeneous structure characterized by zones significantly diilering in chemical composition in contiguous zones, the boundary between the Zones being distinct, and preferably irregular. The surface of the bonded body is anodized under suitable conditions to emphasize the non-uniform structure -of the body thereby revealing a variegated pattern of contrasting shades or color raising from the marked difference in chemical composition of the contiguous zones. For a better understanding of my invention, reference is made herein to the accompanying figures of typical wrought products made in accordance with my invention as described in greater detail in the examples set forth below and revealing a variegated pattern.

Where the body formed upon consolidation of the particulate is subsequently worked by such elongated metal working operations as extrusion or rolling, a pattern of alternating streaks of discontinuous and variable length and width is revealed in the final product. However, a cross-section or beveled edge of the worked product reveals a mottled pattern. Regardless of whether the pattern may best be described as variegated, striated, or mottled, which terms I use synonymously, it is significant that the pattern is intrinsic or built-in the product, and consequently 'of a permanent nature. This is in contrast, for example, to the ordinary decorative aluminum surface made by dyeing or pigmenting an artifically-produced oxide coating.

The variegated pattern is markedly exhibited in an aluminous product formed from a compact of a mixture of particulate from the group of (1) aluminum and at least one aluminum base alloy, and (2) aluminum base alloys. The particulate are relatively small as compared to the final product but yet of suflicient size to result in a body of non-uniform structure exhibited upon proper surface treatment. The particulate employed as base material for the compact include, for example, granulated ingot, impact extrusion slugs, machined chips, pieces stamped from sheet and turnings. The preferred material is granulated ingot which is formed by allowing drops or globules of the molten metal to solidify upon immersion in a relatively cool medium such as water. It is preferable to employ particulate that is irregular in shape and size which 'adds substantially to the variegated effect in the final product. However, it

3,1 13,002 Patented Dec. 3, 1963 is desirable to avoid an excessive amount of irregularity in the size and shape of particulate because it is more difficult to mix and consolidate than regularly shaped particulate.

The particulate employed in forming the compact may comprise an admixture of particulate of aluminum and one or more aluminum base alloys, or simply an admixture of particulate of aluminum base alloys Particurlate of aluminum is intended to include pure aluminum or commercial aluminum containing the usual incidental impurities. Particulate of aluminum base alloys may include an admixture of particulate containing the same alloying constituent or constituents present in varying proportions, or an admixture of particulate containing different alloying constituents. The admixture of particulate may be selected in accordance with the texture and effects in color and shades desired in the final product as explained hereafter in greater detail.

'In accordance with my invention, the variegated pattern imparted to the wrought product depends essentially upon the composition of the particulate employed. Zones in the final product formed from particulate of aluminum exhibit a metallic luster or shade. "Shades varying from very light to dark gray or black may be produced in the final wrought product by employing particulate containing alloying elements from the group consisting essentially of iron and silicon. Thus, the gray shades are produced from an alloy consisting essentially of 0.5 to 3% by weight iron, and preferably 1.5 to 2%, or similarly from an alloy consisting essentially of l to 20% by Weight silicon, and preferably of 4.5 to 7.5%, the balance in each case being substantially aluminum. An alloying content outside these described ranges results in a loss of contrast of gray shades in the pattern. Employing particulate in the as-cast condition of an aluminum-iron alloy containing about 2% iron or more, or an aluminum-silicon alloy containing about 5% silicon or more, results in a substantially black color in the final product. The black color may be fiurther modified to a gray shade upon suitable heat treatment at a temperature of from about 600 to l060 F., and varying periods of time of from a few minutes to several hours, the shade of gray becoming lighter with increasing temperature and time. Heat treating above 1060 F. generally results in a loss in the gray shade in the final product.

In addition, a bluish tone may be imparted to the finished product by employing particulate of an aluminumiron alloy, containing :as an additional constituent about 0.1 to 1% by weight cobalt. On the other hand, the gray tones of the aluminum-iron alloys may be somewhat modified by the addition of 0.1 to 1% by weight nickel. Particulate of aluminum-iron alloy or aluminum-silicon alloy may contain, in addition, about 0.1 to 1% by weight magnesium and 0.1 to 5% by weight zinc without obscuring or masking the contrast in pattern, but the iron or silicon content preferably equals or exceeds the content of these elements.

Employing particulate of aluminum base alloys con taining alloying elements selected from the group con' helpful. If desired 0.1 to 1% by weight of manganese can be included.

In forming the wrought product, the aluminous particulate may be initially formed into a compact that is subsequently worked, or the particulate may be charged directly to a compression chamber such as an extrusion press cylinder and be extruded therefrom after initial consolidation of the mass. The initial compact may be made by heating the particulate to a temperature between about 600 and 1060 F. and applying a sufiicient pressure thereto for a long enough period of time to cause at least some consolidation and welding of the particulate. Pressures of 20,000 to 200,000 pounds per square inch are generally satisfactory, a longer period of time being required where low pressures are employed. The compact formed may be left in the press cylinder and then extruded, or it may be ejected, cooled, scalped, reheated to the hot working temperature and hot worked. In some cases it may be desirable to reheat the compact to temperatures as high as 1060 F. before hot working in order to obtain adequate workability. Where the particulate are charged to a compression chamber, the particulate may be initially heated to a temperature between 600 and 1060 F. and introduced to the chamber or simply charged cold and heated within the chamber. Alternatively, the particulate may be heated to an intermediate temperature, then charged to the chamber and brought to the desired temperature. When the particulate are to be compacted and immediately extruded, it is generally convenient to compress the particulate against a blind die in a press cylinder and then substitute an extrusion die for it to produce the desired extruded shape. Although reference has been made to the extrusion of the particulate, it is to be understood that the particulate can be subjected to other types of hot working operations, such as rolling, forging or pressing, providing a suitable compact is initially produced. The hot working is preferably produced within the temperature range of 600 to 1060 F.

The variegated pattern is fully developed upon the anodic oxidation of the surface whereby the aluminous product is made the anode in a conventional acid electrolyte such as 15% aqueous sulfuric acid solution. When an extruded product is anodized, a Variegated pattern will appear because of the non-uniform structure of the product. Contrast in the variegated pattern is somewhat proportional to the thickness of the oxide coating produced, the thicker oxide coatings resulting in a greater contrast. To insure adequate protection and performance for outdoor application, however, the oxide coating should not be substantially thinner than about 0.8 mil.

It is generally desirable to seal the oxide coating on aluminum surfaces, as by immersing the surface in boiling water for about 5 to minutes. Sealing renders the coating non-porous and prevents staining or undesired coloring of the coating. However, in certain instances, a five minute seal in a boiling nickel acetate solution having a concentration from about 1 to 5 grams of nickel acetate per liter of water may be more completely effective.

Articles made in accordance with my invention are decorative in appearance, and are particularly useful in architectural applications such as metal Wall and door panels, pilasters, bars, display counters, and the like.

My invention is illustrated by the following examples wherein 10 pound mixtures of granulated ingot of aluminum and certain aluminum base alloys were employed as the color base materials as shown in the following table:

Table I.C0l0r Eflects of Difierent Elements Heat treated 16 hours at 950 F. Heat treated 16 hours at 1050 The mixture of granulated ingot was heated to 800 F., and charged to an extrusion press cylinder also preheated to 800 F., the cylinder having an inside diameter of 4% inches. A bar 16 feet in length was extruded at a rate of about 17 feet per minute and at 36,300 pounds per square inch. The die employed was substantially triangular shaped having arcuate corners, the legs of the triangle being approximately 1 inch in length and the base about A3 inch. One end of the bar was beveled as shown in FIGURE 1. The extruded bar was treated by conventional practice to brighten the surface by immersing the bar for about 3 minutes in an aqueous solution of phosphoric acid and nitric acid commonly employed in the aluminum industry. The bar was then anodized in a 15% sulfuric acid electrolyte for to minutes with a current density of 12 amperes per square foot, the temperature of the electrolyte being F. A decorative, variegated pattern of contrasting shades of color was exhibited on the exposed surfaces of the extrusion, the colors being those set forth in the above table. FIGURE 1 is a photograph of the wrought product showing the variegated pattern (except for the gold color which cannot be shown in a black and white photograph).

In a second example, a mixture of clippings of aluminum sheet containing different amounts of iron was em ployed as the base material. The different alloys and their relative proportions in the mixture are shown in the following table:

Lbs. Em-

ployed in the Mixture Color in Final Pmduct Attributable to Base Material Percent Iron Black.

The clippings of the alloys were mixed thoroughly, heated to about 700 F., and charged to an extrusion press cylinder having an inside diameter of 4% inches and also preheated to 700 F. The clippings of sheet were compacted against a blind die for 1 minute at 177,200 pounds per square inch. An extrusion die having an opening of 2.3 inches in diameter was substituted for the blind die, and a rod 1.7 feet long (excluding the ex trusion butt) was extruded at a rate of 0.46 feet per minute, at 700 F. under a pressure of 30,800 pounds per square inch. The extruded rod was cut to lengths of 0.6 inch and then machined to a diameter of 1.980 inch to form impact extrusion slugs. The slugs were annealed for one hour at 900 F, inserted in an impact extrusion press and extruded into the form of a cylinder with a closed bottom. The surfaces of the cylinder were then brightened with the phosphoric acid-nitric acid solution and anodized, as in the previous example. The decorative pattern or" contrasting gray and black shades was exhibited, as shown in FiGURE 2.

Having thus described my invention and certain cmbodiments thereof, 1 claim:

1. A decorative anodically coated wrought aluminous metal product having a heterogeneous structure throughout the body of said product and exhibiting a variegated pattern at the surface thereof, said product being formed by the consolidation and bonding of aluminous metal particulates of a size represented by the range of that of machined chips to impact extrusion slugs of at least two different chemical compositions and characterized by contiguous zones having distinct boundaries therebetween, said zones having compositions corresponding to that of the said particulates.

2. The product according to claim 1 wherein the particulates are composed of aluminum and at least one aluminum base alloy.

3. The product according to claim 1 wherein the particulates are composed of at least two different aluminum base alloys.

4. The product according to claim 1 wherein the particulates are composed of two aluminum base alloys, one consisting essentially of aluminum and 0.5 to 3% by weight of iron and the second one consisting essentially of aluminum and 1 to 20% by weight of silicon.

5. The product according to claim 1 wherein the particulates are composed of two aluminum base alloys, one consisting essentially of aluminum and 0.5 to 3% by weight of iron and the second alloy consisting essentially of aluminum and 0.1 to 0.5% by weight of chromium.

6. The product according to claim 1 wherein the particulates are composed of two aluminum base alloys, one consisting essentially of aluminum and 1 to 20% by weight of silicon and the second alloy consisting essentially of 0.1 to 0.5% by weight of chromium.

7. An anodically coated wrought aluminous metal product having a heterogeneous structure and exhibiting a variegated pattern at the surface, said product being formed by the consolidation and bonding of aluminous metal particulates of a size represented by the range of that of machined chips to impact extrusion slugs of at least two dilferent aluminum-iron alloys containing iron within the range of 0.5 to 3% by weight, and character- 6 ized by contiguous zones having distinct boundaries therebetween, said zones having compositions corresponding to that of said aluminum-iron alloy particulates.

8. A decorative anodically coated Wrought aluminous metal product having a heterogeneous structure throughout the body of said product and exhibiting a variegated pattern at the surface thereof, said product being formed by the consolidation and bonding of aluminous metal particulates of a size represented by the range of that of machined chips to impact extrusion slugs of at least two dilferent aluminum-silicon alloys containing silicon within the range of 1 to 20% by weight, and characterized by contiguous zones having distinct boundaries therebetween, said zones having compositions corresponding to that of said aluminum-silicon alloy particulates.

References Cited in the file of this patent UNITED STATES PATENTS Re. 16,340 Backer May 4, 1926 1,893,330 Jones Ian. 3, 1933 2,390,183 Seligman Dec. 4, 1945 2,391,752 Stern Dec. 25, 1945 2,662,034 Mason et al. Dec. 8, 1953 2,809,891 Ennor et al. Oct. 15, 1957 2,941,282 Fromson June 21, 1960 

1. A DECORATIVE ANODICALLY COATED WROUGHT ALUMINOUS METAL PRODUCT HAVING A HETEROGENEOUS STRUCTURE THROUGHOUT THE BODY OF SAID PRODUCT AND EXHIBITING A VARIEGATED PATTERN AT THE SURFACE THEREOF, SAID PRODUCT BEING FORMED BY THE CONSOLIDATION AND BONDING OF ALUMINOUS METAL PARTICULATES OF A SIZE REPRESENTED BY THE RANGE OF THAT OF MACHINED CHIPS TO IMPACT EXTRUSION SLUGS OF AT LEAST TWO DIFFERENT CHEMICAL COMPOSITIONS AND CHARACTERIZED BY CONTIGUOUS ZONES HAVING DISTINCT BOUNDARIES THEREBETWEEN, SAID ZONES HAVING COMPOSITION CORRESPONDING TO THAT OF THE SAID PARTICULATES. 